A 12-game winning streak is on the line for Penrith without seven State of Origin stars and 631 NRL games of experience against the Wests Tigers on Friday.
The Panthers have written history out west with their unbeaten start to the season but will face the biggest test of the year against their new, but fierce, rivals.
Ivan Cleary's return to Leichhardt Oval will be the first time he's coached at the Tigers' spiritual home since walking out on a contract with the club to join the Panthers at the end of 2018.
But he's going into battle with a team low on troops with seven players missing through State of Origin duty, including skippers Isaah Yeo and Nathan Cleary.
It's a void of leadership he hopes will be filled by senior players Viliame Kikau and James Fisher-Harris, who has been named captain in the absence of the Blues stars.
It's one of the most inexperienced teams Cleary has coached.
"I did the maths today ... there's only about 600 NRL games in this team," he said on Thursday.
"About 1000 is really low. We're a young team anyway, we're a young club."
Fullback Dylan Edwards returns from injury while Matt Burton and Tyrone May replace Cleary and Jarome Luai in the halves with Mitch Kenny at hooker.
Lindsay Smith and Izack Tago have been named to make their NRL debut from the bench.
"It's a great challenge, it's a test of culture on our systems," Cleary said.
"We've got guys making our debut and some guys who haven't played a lot of first grade so it's super exciting.
"We just stick to what we do, we run the same systems in reserve grade so they're used to playing this style of footy.
"They've got to do what they do every week, be who they are, work together as a team."
Meanwhile, the Tigers are coming off a good win against St George Illawarra but have not been able to win back-to-back games since the start of last season.
Coach Michael Maguire, then, is not falling into a trap of believing Penrith will be easier to beat if they're depleted.
"They're a good team and they've obviously been doing it for a long time, so it's about what we need to do," he said.
"We need to turn up with the right frame of mind."